1. Field of the Invention
The present invention relates to a gas treatment apparatus for gelatinizing a coated film coated on the front surface of a substrate and forming an insulation film, the coated film being formed by dispersing particles or colloid of a start substance of a film component to solvent.
2. Description of the Related Art
As methods for forming an inter-layer insulation film of a semiconductor device, CVD method, heat oxidizing method, and so forth are known. In addition, sol-gel method is known. In the sol-gel method, a coating solution of which colloid of TEOS (tetraethoxysilane: Si(C2H5O)4) is dispersed in organic solvent such as ethanol solution is coated on the front surface of a semiconductor wafer (hereinafter simply referred to as wafer). The coated film is gelatinized and dried. Thus, a silicon oxide film is obtained. An example of such a method has been disclosed in Japanese Patent Laid-Open Publication Nos. 8-162450 and 8-59362.
FIGS. 9A, 9B, and 9C show degeneration of a coated film in such a method.
When a coating solution is coated on a wafer, particles or colloid 100 of TEOS is dispersed to solvent 200 (refer to FIG. 9A). Thereafter, the coated film is exposed to alkaline atmosphere or heated. Thus, since TEOS is polycondensated and hydrolyzed, the coated film is gelatinized and thereby a mesh structure of TEOS 300 is formed (refer to FIG. 9B). The solvent of the coated film is substituted with another solvent 400 such as acetone so as to remove moisture from the coating solution (refer to FIG. 9C). The solvent substituting treatment is a hydrophobic treatment for the film. In other words, since an OH radical tends to absorb moisture, when the film is reacted with for example HMDS, the OH radical bound to an edge portion of Sixe2x80x94O coupling is substituted with another organic substance.
After the coating solution is dried, a coated film of silicon oxide film is obtained. Moreover, in the solvent substituting treatment shown in FIG. 9C, solvent whose surface tension is smaller than that of ethanol is used. Thus, when the solvent vaporizes, since large stress is not applied to the mesh structure of TEOS, the film can be prevented from breaking.
The silicon oxide film formed by the sol-gel method has many air pores. Thus, the dielectric constant E of the oxide film is very close to that of vacuum. Consequently, the electric resistance of the oxide film having air pores is as high as that of vacuum. As a result, an ideal insulation film can be obtained.
When the sol-gel method is applied to a real production line, a coating unit that coats a coating solution to a wafer, an aging unit that contacts ammonium gas to the wafer or heats the wafer at a predetermined temperature (for example, around 100xc2x0 C.) and gelatinizes the coated film, and a substituting unit that substitutes the solvent of the coated film with another solvent are required.
In the gelatinizing treatment performed by the inventor of the present invention, as shown in FIG. 10, a wafer W is placed on a plate 61. A cylindrical lid 62 is placed on the plate 61. Thus, a sealing vessel 6 is formed. Ammonium gas is supplied from a gas supplying path 63 on the periphery of the plate 61. The ammonium gas is exhausted from an exhausting path 64 at the center of the lid 62.
In the unit shown in FIG. 10, the ammonium gas tends to upwardly flow from the gas supplying opening of the plate 61 along the inner periphery of the lid 62 upwardly. In addition, the ammonium gas is attracted by attracting force of the exhausting path 64 at the center of the lid 61. Thus, a gas flow takes place in an upper diagonal direction. Since gas that upwardly flows along the inner periphery of the lid 62 becomes a vortex flow at upper corners of the lid 62, the gas does not smoothly lower. Thus, the gas flow rate and gas concentration at the center portion of the wafer W are smaller than those at the peripheral portion thereof. Consequently, the coated film is unevenly gelatinized and thereby an unsmooth film is formed.
A first aspect of the present invention is made from the above-described point of view.
An object of the first aspect of the present invention is to provide a coated film treatment apparatus that allows a substrate (for example, a wafer) to be treated with an equal gas flow in a sealing vessel so as to obtain a high-quality thin film (for example, an inter-layer insulation film).
A first aspect of the present invention is a gas treatment apparatus, comprising a sealing vessel for treating a substrate with gas, a substrate holding portion, disposed in the sealing vessel, for holding the substrate, a gas flow regulating surface portion, disposed opposite to a treatment surface of the substrate held on the substrate holding portion, the gas flow regulating surface portion protruding to the substrate holding portion and having at least an outer peripheral portion for forming a narrowed gas path with the substrate holding portion, a gas supplying opening disposed along a peripheral portion of the gas flow regulating surface portion, and an exhausting opening facing the treatment surface of the substrate held on the substrate holding portion and disposed at a center portion of the sealing vessel.
The gas treatment apparatus may further comprises a buffer chamber disposed outside the outer peripheral portion and at an upper portion of the gas supplying opening.
An inner periphery of the gas flow regulating surface portion may be composed of a first concave portion formed in almost a spherical surface shape, a convex portion formed inside the first concave portion and protruding in an almost doughnut shape, and a second concave portion formed in an almost circular cone shape inside the convex portion and connected to the exhausting opening wherein the first concave portion, the convex portion, and the second concave portion are inwardly and continuously formed on concentric circles.
The outer peripheral portion may be a partition plate that partitions an inner space of the sealing vessel into a cylindrical space facing the treatment surface of the substrate held on the substrate holding portion and a buffer chamber formed outside the cylindrical space. In addition, an inner periphery of the gas flow regulating surface portion may be composed of an outer portion formed in an almost plane shape, an inclined portion formed inside the outer portion, the inclined portion forming a side surface of an almost circularly cone shaped protrusion portion, a convex portion formed in an almost doughnut shape inside the inclined portion, and a concave portion formed in an almost circularly cone shape inside the convex portion and connected to the exhausting opening wherein the outer portion, the inclined portion, and the convex portion, and the concave portion are inwardly and continuously formed on concentric circles.
An almost spherical surface shaped concave portion may be formed on an inner periphery of the gas flow regulating surface portion.
A circularly cone shaped concave portion with a vertex of the exhausting opening may be formed on an inner periphery of the gas flow regulating surface portion.
The outer peripheral portion may form a partitioning portion with a cylindrical section wherein an inner periphery of the gas flow regulating surface portion is a plane with almost the same height as a vertex portion of the buffer chamber.
An inner periphery of the gas flow regulating surface portion may be composed of a first concave portion formed in almost a spherical surface shape, a convex portion formed inside the first concave portion and protruding in an almost doughnut shape, and a second concave portion formed in an almost circular cone shape inside the convex portion and connected to the exhausting opening wherein the first concave portion, the convex portion, and the second concave portion are inwardly and continuously formed on concentric circles.
The gas supplying opening may be formed in a slit shape along a peripheral direction of the sealing vessel.
The sealing vessel may be composed of a first member on which the substrate holding portion is disposed, and a second member on which the gas flow regulating surface portion is disposed, the second member being approachable to the first member.
The gas supplying path may be formed through the first member.
A coating solution of which particles or colloid of a start substance of a film component is dispersed to solvent may be coated as a coated film on the substrate wherein gas for accelerating gelatinizing the particles or colloid of the coated film is supplied to the sealing vessel.
The gas is preferably alkaline gas.
Next, a second aspect of the present invention will be described.
When a wafer on which coating solution has been coated as shown in FIGS. 9A, 9B, and 9C is left in a natural condition, the coating solution is gelatinized and a silicon oxide film is formed.
However, to do that, it takes a long time (for example, one night). Thus, such a method is not suitable from a view point of mass-production. As the second aspect of the present invention, a coated film is heated so as to acceleratingly gelatinize it.
When a wafer on which a coated film has been formed is heated at for example around 100xc2x0 C. and the coated film is gelatinized, since organic solvent vaporizes from the coated film, a predetermined film thickness and film quality cannot be obtained. To solve such a problem, a wafer is placed in a sealing vessel. Saturated vapor of a solvent component (for example, ethylene glycol) of the coated film is supplied to the sealing vessel. Thus, ethylene glycol can be suppressed from vaporizing from the coated film.
In this case, saturated vapor of ethylene glycol at 100xc2x0 C. is generated and supplied to the sealing vessel that is heated at 100xc2x0 C. Thus, ethylene glycol can be suppressed from vaporizing. However, when the temperature of gas in a pipe to the sealing vessel drops, condensation takes place. Thus, the saturated vapor cannot be obtained in the sealing vessel. As a result, the solvent component (in this case, ethylene glycol) of the wafer vaporizes. On the other hand, when the temperature of the saturated vapor of ethylene glycol is higher than that in the sealing vessel, the temperature of the saturated vapor drops in the sealing vessel. Thus, concentration may take place and thereby liquid drops may adhere to the wafer. When liquid drops adhere to the wafer, the film thickness at the liquid adhered position varies. Thus, the equality of the film thickness deteriorates. Consequently, in addition to the temperature control of the generation source of the saturated vapor of the solvent component, saturated vapor should be generated in the treatment vessel.
The second aspect of the present invention is made from the above-described point of view.
In other words, an object of the second aspect of the present invention is to provide a gas treatment apparatus that allows a solvent component to be suppressed from vaporizing from a coated film in gelatinizing particles or colloid of the coated film so as to obtain a film (for example, an inter-layer insulation film) with a predetermined film thickness.
A second aspect of the present invention is a gas treatment apparatus, comprising a sealing vessel for holding a substrate coated with a coating solution of which particles or colloid of a start substance of a film component is dispersed to solvent, a heating means for heating the inside of the sealing vessel so as to gelatinize the particles or colloid of a coated film as the coating solution, a gas supplying path for supplying vapor of a solvent component to the sealing vessel, an exhausting path for exhausting gas out of the sealing vessel, a gas dispersing chamber disposed in the middle of the gas supplying path in a wall of the sealing vessel, the gas dispersing member, having a plurality of gas supplying openings, connected to the sealing vessel, for dispersing gas in the gas supplying path to the sealing vessel, the inner temperature of the gas dispersing chamber being kept at almost the same as the inner temperature of the sealing vessel, and a solvent vapor generating portion, heated at a slightly higher temperature than the inner temperature of the gas dispersing chamber, for generating vapor of the solvent component that becomes saturated vapor at the inner temperature of the sealing vessel.
According to the second aspect of the present invention, saturated vapor of a solvent component (for example, ethylene glycol) generated by the solvent vapor generating portion is slightly cooled in the gas dispersing chamber to the almost the same temperature in the sealing vessel. Thus, saturated vapor is securely supplied to the sealing vessel. Consequently, the solvent is suppressed from vaporizing from the coated film. In addition, liquid drops of the vapor are prevented from adhering to the substrate. In this case, the sealing vessel may have a heating plate for holding and heating the substrate. The gas dispersing chamber may be formed in the heating plate.
A modification of the second aspect of the present invention is a gas treatment apparatus, comprising a sealing vessel for holding a-substrate coated with a coating solution of which particles or colloid of a start substance of a film component is dispersed to solvent, a heating means for heating the inside of the sealing vessel so as to gelatinize the particles or colloid of a coated film as the coating solution, a gas supplying path for supplying vapor of a solvent component to the sealing vessel, an exhausting path for exhausting gas out of the sealing vessel, a first reservoir tank for reserving solution of the solvent component, bubbling the solution with carrier gas, and supplying vapor of the solvent component to the sealing vessel trough the gas supplying path, a first temperature adjusting means for adjusting the temperature of the solution in the first reservoir tank to a predetermined temperature, a second reservoir tank for replenishing the solution to the first reservoir tank when the amount of the solution in the first reservoir tank decreases, and a second temperature adjusting means for adjusting the temperature of the solution in the second reservoir tank to a predetermined temperature.
According to the present invention, the temperature of the solution of the solvent component can be accurately controlled. Thus, the vapor of the solvent component at a predetermined temperature can be supplied to the sealing vessel. In the present invention, alkaline gas for accelerating gelatinizing the coated film may be supplied to the sealing vessel.